1. Field
The present invention relates to composite materials. More particularly, the invention relates to tensioning composite material during a curing process.
2. Related Art
Composite parts for use in airplanes and other applications may be made from braided preform composite material that undergoes forming and curing processes. Forming and curing processes may involve, for example, severing a piece of braided preform composite material from a mandrel; securing the material to a mold, such as a cure tool surface; impregnating the material with resin; positioning an airtight lining, such as a cure bag, over the composite material and resin; creating a vacuum between the airtight lining and the mold surface to compress the material and resin; and applying heat to the material, resin, and airtight lining. The mold may include a C-channel, typically comprising an elongated channel with a bottom wall, an inner upwardly extending side wall, and an outer upwardly extending side wall.
The C-channel can be curved in various planes, and the upwardly extending side walls may be integrally formed or otherwise joined to the bottom wall at 90° angles or non-90° angles. In one instance, the C-channel is curved along its length with the inner wall formed along an inner radius of the curve and the outer wall formed along an outer radius of the curve. When material is pressed against inner surfaces of the C-channel and then tensioned and compressed, undesirable wrinkles or aberrations can form in the material. This is due to the difference in path lengths between the material at the inner radius of the curve and the material at the outer radius of the curve. These wrinkles are more pronounced closer to a side edge of the material along the inner radius. In a curved C-channel, wrinkles typically form along the inner wall.